Efficient way to remove objects from a list

M.-A. Lemburg mal at egenix.com
Mon Nov 3 12:12:43 CET 2008


> 一首诗 wrote:
>> Hi all,
>>
>> Today I wrote some code like this:
>>
>>         for m in self.messages:
>>             if not m.finished:
>>                 continue
>>
>>             #process the message
>>
>>         fini = [m for m in self.messages if m.finished]
>>         for m in fini:
>>             self.messages.remove(m)
>>
>> As you can, I want to find these finished messages in
>> "self.messages",
>> process them, and then remove them from the list.
>>
>> Because a list can not be modified while iterating it,  I have to use
>> a list "fini" to accomplish the target.
>>
>> I found a smell of bad performance here.
>> Is there any faster ways?

The typical way to do this is to iterate over the list in reverse
order and then using the item index as basis for removing the
item:

for i, item in enumerate(reversed(mylist)):
    # process item
    del mylist[i]

-- 
Marc-Andre Lemburg
eGenix.com

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